Justification:
This species is listed as Endangered because its extent of occurrence is less than 1,000 km2, area of occupancy probably is less than 100 km2, the species occurs in 4 locations, and populations are subject to ongoing threats (habitat dewatering) that may quickly reduce or eliminate subpopulations.

Range includes a small area of the Tularosa Basin, southern New Mexico (Page and Burr 2011). Natural populations occur in the Salt Creek drainage (Malpais Spring, a brackish spring; Salt Creek, a saline river), in Otero, Sierra, and Lincoln counties, all within the White Sands Missile Range (Pittenger and Springer 1999). The species was presumably introduced at Holloman Air Force Base and White Sands National Monument near Alamogordo in a short spring-fed section of Malone Draw (Lost River), Otero County (Echelle et al. 1987, Springer 1996); the Mound Spring population (Salt Creek drainage) also is derived from translocations from the Salt Creek population (Stockwell et al. 1998). During wet years, the Lost River population may occupy habitat within White Sands National Monument. Greatest observed abundance is in localized reaches of 40 kilometres of occupied habitat in Salt Creek, disjunct sections of Lost River (Malone Draw), and upper portions of Malpais Spring; numbers are relatively low in Mound Springs (Sublette et al. 2011). An introduced population in a sewage-enriched pond west of Alamogordo was extirpated when the pond dried in 1976 (Jester and Suminski 1982). The entire range is included in an area of approximately 15 by 60 kilometres in the bottom of the Tularosa Basin (Jester and Suminski 1982).

This species occurs in four isolated desert spring systems (Pittenger and Springer 1999).

Total adult population size is unknown but presumably exceeds 100,000 and probably at least sometimes exceeds 1,000,000. This species is relatively abundant in most of its limited range (Pittenger and Springer 1999).

Population monitoring using catch per unit effort as a relative index of pupfish abundance detected a substantial decline in the introduced population at Mound Spring in 1995 whereas the other three habitats supported very large populations (Pittenger and Springer 1996).

Populations exhibit wide fluctuations in abundance. Overall abundance in Malpais Spring, Salt Creek, and Lost River depends on extent of wetted habitats. Increased wetted areas as a consequence of storm events was accompanied by increased abundance of White Sands pupfish (Propst 1999).

Trend over the past 10 years or three generations is uncertain but likely to be relatively stable, with seasonal fluctuations.

Habitat includes warm springheads, outlet streams, and associated marshes (Minckley et al. 1991). This species typically occurs in clear, shallow water over a variety of substrates, ranging from sand and gravel to silt and mud. Pools and creeks are highly mineralized and charged with alkali and salt (Lee et al. 1980). Salt Creek and Lost River are subject to periodic flash flooding. Aquatic vegetation may be present; associated species include Scirpus, Ruppia, Potamogeton, Typha, Eleocharis, and Characeae; adjacent terrestrial vegetation is typically sparse except for Distichlis and Tamarix (Sublette et al. 1990). The pupfish occurs in spatially variable habitats and can tolerate a wide range of salinities and temperatures. In Lost River, larger individuals were in areas of lower salinity, but more fish were found in areas of high salinity, high temperature, shallow water, and low volume; whether this pattern resulted from habitat preferences or intraspecific competitive interactions is unknown (Rogowski et al. 2006). Spawning occurs in the shallow periphery of the habitat.

Primary potential threats are natural changes or human activities that cause either dewatering or other alterations of habitat and introduction of exotic fishes (Sublette et al. 1990). Threats have been reduced by implementation of a conservation agreement involving all appropriate agencies, but extremely limited range extent and area of occupancy makes this species vulnerable to extinction from natural and anthropogenic causes (White Sands Pupfish Conservation Team 2006).

Habitat is naturally devoid of other aquatic vertebrates and large, predatory aquatic invertebrates. Experimental studies indicate that introductions of non-native species such as mosquitofish and crayfish would be detrimental to pupfish populations (Rogowski and Stockwell 2006).

In the 1990s, the main threats were regarded as a feral horse population (damages aquatic habitats), military activities, weapons testing, and introduction of non-native fishes, particularly predators (New Mexico Department of Game and Fish 1996). The feral horse population at White Sands Missile Range has been reduced.

Maintenance of the limited habitat is essential, as is exclusion of exotic species (see White Sands Pupfish Conservation Plan, Propst and Pittenger 1994; see also White Sands Pupfish Conservation Team 2006).

White Sands Missile Range, USFWS, New Mexico Department of Game and Fish, White Sands National Monument, and Holloman Air Force Base are cooperating in carrying out a conservation plan (Stuart 1995, Springer 1996, White Sands Pupfish Conservation Team 2006). The plan calls for introducing this fish into additional waters in the Tularosa basin and control of populations of non-native fishes on the missile range; water withdrawals from pupfish habitat are prohibited.

Collyer et al. (2005) found significant body shape variation among native and introduced populations. The significant shape divergence of introduced populations warrants consideration for the conservation of this rare species, as creation of refuge populations for native stocks is a current management strategy (Collyer et al. 2005).

White Sands Pupfish Conservation Team includes representatives from 5 resource management agencies (Holloman Air Force Base, White Sands Missile Range, White Sands National Monument, U. S. Fish and Wildlife Service, and New Mexico Department of Game and Fish). This team has been charged with developing and implementing the White Sands Pupfish Conservation Plan (Propst and Pittenger 1994).

Existing conservation plan call for the development of monitoring programs for the fish and its habitat.